Store last modified time in project storage + retrieve it

Author: wonder-sk

python/core/qgsprojectstorage.sip.in

@@ -24,6 +24,20 @@ and registered in QgsProjectStorageRegistry.
 #include "qgsprojectstorage.h"
 %End
   public:
+
+    class Metadata
+{
+%Docstring
+Metadata associated with a project
+%End
+
+%TypeHeaderCode
+#include "qgsprojectstorage.h"
+%End
+      public:
+        QDateTime lastModified;
+    };
+
     virtual ~QgsProjectStorage();
 
     virtual QString type() = 0;
@@ -63,6 +77,12 @@ was successful.
 %Docstring
 Rename an existing project at the given URI to a different URI. Returns true if renaming
 was successful.
+%End
+
+    virtual bool readProjectMetadata( const QString &uri, QgsProjectStorage::Metadata &metadata /Out/ );
+%Docstring
+Reads project metadata (e.g. last modified time) if this is supported by the storage implementation.
+Returns true if the metadata were read with success.
 %End
 
     virtual QString visibleName();

src/core/qgsprojectstorage.h

@@ -17,7 +17,9 @@
 #define QGSPROJECTSTORAGE_H
 
 #include "qgis_core.h"
+#include "qgis_sip.h"
 
+#include <QDateTime>
 #include <QString>
 
 class QIODevice;
@@ -34,6 +36,14 @@ class QgsReadWriteContext;
 class CORE_EXPORT QgsProjectStorage
 {
   public:
+
+    //! Metadata associated with a project
+    class Metadata
+    {
+      public:
+        QDateTime lastModified;
+    };
+
     virtual ~QgsProjectStorage();
 
     /**
@@ -73,6 +83,12 @@ class CORE_EXPORT QgsProjectStorage
      */
     virtual bool renameProject( const QString &uri, const QString &uriNew ) { Q_UNUSED( uri ); Q_UNUSED( uriNew ); return false; }
 
+    /**
+     * Reads project metadata (e.g. last modified time) if this is supported by the storage implementation.
+     * Returns true if the metadata were read with success.
+     */
+    virtual bool readProjectMetadata( const QString &uri, QgsProjectStorage::Metadata &metadata SIP_OUT ) { Q_UNUSED( uri ); Q_UNUSED( metadata ); return false; }
+
     /**
      * Returns human-readable name of the storage. Used as the menu item text in QGIS. Empty name
      * indicates that the storage does not implement GUI support (showLoadGui() and showSaveGui()).

src/providers/postgres/qgspostgresprojectstorage.cpp

@@ -6,8 +6,32 @@
 #include "qgsreadwritecontext.h"
 
 #include <QIODevice>
+#include <QJsonDocument>
+#include <QJsonObject>
 #include <QUrl>
 
+
+static bool _parseMetadataDocument( const QJsonDocument &doc, QgsProjectStorage::Metadata &metadata )
+{
+  if ( !doc.isObject() )
+    return false;
+
+  QJsonObject docObj = doc.object();
+  metadata.lastModified = QDateTime();
+  if ( docObj.contains( "last_modified_time" ) )
+  {
+    QString lastModifiedTimeStr = docObj["last_modified_time"].toString();
+    if ( !lastModifiedTimeStr.isEmpty() )
+    {
+      QDateTime lastModifiedUtc = QDateTime::fromString( lastModifiedTimeStr, Qt::ISODate );
+      lastModifiedUtc.setTimeSpec( Qt::UTC );
+      metadata.lastModified = lastModifiedUtc.toLocalTime();
+    }
+  }
+  return true;
+}
+
+
 static bool _projectsTableExists( QgsPostgresConn &conn, const QString &schemaName )
 {
   QString tableName( "qgis_projects" );
@@ -123,13 +147,18 @@ bool QgsPostgresProjectStorage::writeProject( const QString &uri, QIODevice *dev
   // read from device and write to the table
   QByteArray content = device->readAll();
 
-  QString metadata = "{ \"last_modified\": 123 }";  // TODO: real metadata
+  QString metadataExpr = QStringLiteral( "(%1 || (now() at time zone 'utc')::text || %2 || current_user || %3)::jsonb" ).arg(
+                           QgsPostgresConn::quotedValue( "{ \"last_modified_time\": \"" ),
+                           QgsPostgresConn::quotedValue( "\", \"last_modified_user\": \"" ),
+                           QgsPostgresConn::quotedValue( "\" }" )
+                         );
 
   // TODO: would be useful to have QByteArray version of PQexec() to avoid bytearray -> string -> bytearray conversion
   QString sql( "INSERT INTO %1.qgis_projects VALUES (%2, %3, E'\\\\x" );
   sql = sql.arg( QgsPostgresConn::quotedIdentifier( projectUri.schemaName ),
                  QgsPostgresConn::quotedValue( projectUri.projectName ),
-                 QgsPostgresConn::quotedValue( metadata ) );
+                 metadataExpr  // no need to quote: already quoted
+               );
   sql += QString::fromAscii( content.toHex() );
   sql += "') ON CONFLICT (name) DO UPDATE SET content = EXCLUDED.content, metadata = EXCLUDED.metadata;";
 
@@ -164,6 +193,33 @@ bool QgsPostgresProjectStorage::removeProject( const QString &uri )
 }
 
 
+bool QgsPostgresProjectStorage::readProjectMetadata( const QString &uri, QgsProjectStorage::Metadata &metadata )
+{
+  QgsPostgresProjectUri projectUri = parseUri( uri );
+  if ( !projectUri.valid )
+    return false;
+
+  QgsPostgresConn *conn = QgsPostgresConnPool::instance()->acquireConnection( projectUri.connInfo.connectionInfo( false ) );
+
+  bool ok = false;
+  QString sql( QStringLiteral( "SELECT metadata FROM %1.qgis_projects WHERE name = %2" ).arg( QgsPostgresConn::quotedIdentifier( projectUri.schemaName ), QgsPostgresConn::quotedValue( projectUri.projectName ) ) );
+  QgsPostgresResult result( conn->PQexec( sql ) );
+  if ( result.PQresultStatus() == PGRES_TUPLES_OK )
+  {
+    if ( result.PQntuples() == 1 )
+    {
+      QString metadataStr = result.PQgetvalue( 0, 0 );
+      QJsonDocument doc( QJsonDocument::fromJson( metadataStr.toUtf8() ) );
+      ok = _parseMetadataDocument( doc, metadata );
+    }
+  }
+
+  QgsPostgresConnPool::instance()->releaseConnection( conn );
+
+  return ok;
+}
+
+
 QgsPostgresProjectUri QgsPostgresProjectStorage::parseUri( const QString &uri )
 {
   QUrl u = QUrl::fromEncoded( uri.toUtf8() );

src/providers/postgres/qgspostgresprojectstorage.h

@@ -35,6 +35,8 @@ class QgsPostgresProjectStorage : public QgsProjectStorage
 
     virtual bool removeProject( const QString &uri ) override;
 
+    virtual bool readProjectMetadata( const QString &uri, QgsProjectStorage::Metadata &metadata ) override;
+
   private:
     static QgsPostgresProjectUri parseUri( const QString &uri );
 };

tests/src/python/test_project_storage_postgres.py

@@ -28,6 +28,7 @@
     QgsVectorLayer,
     QgsProject,
 )
+from PyQt5.QtCore import QDateTime
 from qgis.testing import start_app, unittest
 from utilities import unitTestDataPath
 
@@ -101,6 +102,15 @@ def testSaveLoadProject(self):
 
         self.assertEqual(len(prj2.mapLayers()), 1)
 
+        # try to see project's metadata
+
+        res, metadata = prj_storage.readProjectMetadata(project_uri)
+        self.assertTrue(res)
+        time_project = metadata.lastModified
+        time_now = QDateTime.currentDateTime()
+        time_diff = time_now.secsTo(time_project)
+        self.assertTrue(abs(time_diff) < 10)
+
         # try to remove the project
 
         res = prj_storage.removeProject(project_uri)